Cellulose, a polysaccharide formed from glucose via β(1,4) glucoside linkages by natural processes (Applied Fiber Science, F. Happey, Ed., Chapter 8, E. Atkins, Academic Press, New York, 1979), has achieved commercial prominence as a fiber as a consequence of the many useful products derived therefrom. In particular, cotton, a highly pure form of naturally occurring cellulose, is well-known for its beneficial attributes in textile applications.
Cellulose exhibits sufficient chain extension and backbone rigidity in solution to form liquid crystalline solutions (U.S. Pat. No. 4,501,886). However, sufficient polysaccharide chain extension has hitherto been achieved primarily in β(1,4) linked polysaccharides. Any significant deviation from that backbone geometry in the glucan polysaccharide family lowers the chain rigidity below that required for the formation of an ordered lyotropic phase. Additionally, it is well-known that important commercial cellulosic fibers such as cotton and rayon increasingly present sustainability issues with respect to land use and environmental imprint.
It is therefore highly desirable to discover other glucose-based polysaccharides with utility in films, fibers and resins largely because of the current emphasis on producing low cost, structural materials from renewable resources. In addition such polymers offer materials that are environmentally benign throughout their entire life cycle.
Poly(α1,3 glucan), a glucan polymer characterized by having α(1,3) glycoside linkages, has been isolated by contacting an aqueous solution of sucrose with a glucosyltransferase (gtfJ) enzyme isolated from Streptococcus salivarius (Simpson et al., Microbiology, 141: 1451-1460, 1995). Glucan refers to a polysaccharide composed of D-glucose monomers linked by glycosidic bonds. Films prepared from poly(α1,3 glucan) tolerated temperatures up to 150° C. and provided an advantage over polymers obtained from β(1,4) linked polysaccharides (Ogawa et al., Fiber Differentiation Methods, 47: 353-362, 1980).
U.S. Pat. No. 7,000,000 disclosed preparation of a polysaccharide fiber comprising hexose units, wherein at least 50% of the hexose units within the polymer were linked via α(1,3) glycoside linkages using the gtfJ enzyme of Streptococcus salivarius. After derivatization, to the acetate ester, the disclosed polymer formed a liquid crystalline solution when it was dissolved above a critical concentration in a solvent or in a mixture comprising a solvent. From this solution continuous, strong, cotton-like fibers highly suitable for use in textiles were prepared and used either in a derivatized form or as a non-derivatized (regenerated) form. The complex and branched glucan, dextran, is used as a primer to initiate poly(α1,3 glucan) synthesis by glucosyltransferase enzymes. During polymerization dextran is incorporated into the structure of poly(α1,3 glucan) creating branches within the poly(α1,3 glucan). The presence of such regions in the poly(α1,3 glucan) can compromise the characteristics of the polymer during fiber spinning and in end use applications. It can therefore be desirable to identify primer molecules, without branches in their structures, which would allow synthesis of highly linear poly(α1,3 glucan) polymers.